1. Field of the Invention
The present invention relates in general to vehicular headlamps, and more particularly to vehicular headlamps of a so-called "projector type" which comprises a light source for producing light, a concave reflector for reflecting the light forward, a shade member located in front of the concave reflector for partially shading and thus contouring the reflected light, and a converging lens located in front of the shade member for projecting the contoured light beam forward. More specifically, the present invention is concerned with a projector type vehicular headlamp which has two light sources installed therein.
2. Description of the Prior Art
In order to clarify the task of the present invention, one conventional projector type headlamp will be described with reference to FIGS. 4 and 5 of the accompanying drawings.
As is schematically illustrated in FIG. 4, the headlamp "a" comprises a concave light reflector "b" which has an ellipsoidal light reflecting surface formed on an inside face thereof. A light source "c", viz., an electric filament, is placed on a first focus "F.sub.1 " of the concave light reflector "b". Thus, light rays emitted from the light source "c" are reflected forward by the reflector "b" and converged at a second focus "F.sub.2 " of the reflector "b". Because the light source "c" has certain dimensions, the bundle of the light rays converged at the second focus "F.sub.2 " has a certain sectional area.
Designated by reference "e" is a shade member which is positioned in the vicinity of the second focus "F.sub.2 " having its upper edge "d" contact with an optical axis "x--x" of the concave light reflector "b".
A converging lens "f" is arranged in front of the shade member "e" in such a manner that a focus "F.sub.c " thereof is placed on the upper edge "d" of the shade member "e".
When the light source "c" is energized and thus produces light rays, the light rays directed rearward are reflected forward by the light reflector "b" and converged at the second focus "F.sub.2 " of the reflector "b". Due to presence of the upper edge "d" of the shade member "e" near the second focus "F.sub.2 ", part of the reflected light rays from the reflector "b" is shaded. Thus, the light beam projected forward from the lens "f" has such a contoured cross-sectional pattern "h" as shown in FIG. 5. That is, the projected beam from the lens "f" has an inverted image of the upper edge "d" of the shade member "e", which thus provides a so-called "low beam". It is to be noted that in FIG. 5, the lines denoted by "H--H" and "V--V" are respective horizontal and vertical lines extending perpendicularly to the optical axis "x--x".
In order to provide the headlamp of this type with an additional function of producing a "high beam", an auxiliary light source "i" is necessary, which is to be arranged behind the main light source "c", as is shown by a broken line in FIG. 4.
However, hitherto, the arrangement of the two light sources in the projector type headlamps has been given little thought. That is, the arrangement has been simply made without deeply considering the measure for carrying out the effective usage of the light rays produced by the auxiliary light source "i". Thus, the headlamp of this type is liable to produce a high beam pattern which lacks a brightness. In fact, due to the inherent arrangement, the high beam pattern projected from the lens "f" is largely spread thereby reducing the luminous flux thereof.